Real time navigation of a virtual camera can be difficult and present technical challenges. A user controlling a virtual camera is typically capable of moving the virtual camera in six (6) degrees of freedom while also changing zoom settings. In some applications the user may also be required to follow a target object or focus on an event in a scene captured by the virtual camera. The target object may be a player running on a field in a sports application for example. The user controlling the virtual camera needs to be skilled in camera navigation in order to produce a visually compelling recording of an event. To become skilled in producing visually compelling video recordings of the event requires training and familiarity with the camera navigation control system as well as creativity in knowing where and when to position the virtual camera.
In the broadcasting industry, particularly for live sports broadcasting, a typical aim is to produce a replay of an event and achieve the replay in the quickest amount of time possible. The requirement for quickly generating a replay puts a high demand upon the user (operator) whose task is to produce these replays. As a result, there may only be a limited number of individuals with the necessary camera navigation skills to perform the replay task in the required time. Some known systems endeavour to reduce the level of operator skill required by use of pre-existing virtual camera paths. However, due to variation between scenes and events, inserting a pre-existing camera path into the scene typically does not result in the event being captured in the desired manner.
One difficulty related to inserting camera paths is, for a camera path to accurately and aesthetically capture an event, an appropriate relationship between the virtual camera's field of view (i.e. the virtual camera's position, orientation, and focal length), and the position of the target object in the scene is required. An appropriate relationship results in the target object being within the field of view of the camera. Replay events are rarely identical, with each event having different target objects, moving in different directions, performing different actions, and at different parts of the scene. In addition, different virtual camera paths are created to capture the different unique events. Inserting a camera path, which had captured one event, to capture another can be unsuccessful in capturing the required events in the scene.
Some known methods endeavour to address the efficiency of producing virtual camera recordings using existing camera paths. One method comprises a user first posing the virtual camera, and then secondly defining multiple parameters specifying how the camera should behave. One of the parameters defines a camera movement type (for example left/right movement, crane movement). The specified camera movement types then affect how the camera moves in relation to the first virtual camera pose. While the method allows the user to pose the camera in relation to a target object, there is little control regarding ensuring the target object is captured as the event progresses.
Another known method utilises a mechanism referred to as a stage. A stage is a pre-authored environment which contains pre-set colours, textures, lighting, camera path, and a drop zone. The drop zone is a 3D volume positioned someplace within the stage where imported objects are placed within. Instead of inserting a camera path into the scene, the camera path is configured to best view the object inserted into the drop zone and the surrounding lighting. While the method using a stage is efficient in quickly utilising existing camera paths (as the paths are already configured into stages), the method is not suitable in the context of live event broadcasting.